Safety device



Sept. 1; 1925. 1,551,900

R. L. MORROW SAFETY DEVICE Filed Dec'. 5. 1924 INVENTOR or sleeve 9 is of conducting material, and

the accumulated charge. As soon as the circuit is broken, the core of the coil 11 be comes demagnetized, and the armature 12 closes the primary circuit again. This opening and closing of the circuit takes place repeatedly in rapid succession, producing an oscillating current in the primary coil 13, which is transformed in the secondary winding 16 into a very-high voltage oscillating current, the voltage depending on the number of turns of wire in the secondary l6 in relationto the number of turns in the'primary 13 and the voltageapplied to the primary. The secondary 16 would normally have thousands of turns. The terminal 17 of the secondary is connected, as directly as possible, to a conductor disposed adjacent the danger point, or preferably to the source of danger itself,- as illustrated, the saw. Terminal 19 is suitably grounded. i

The potential is suflicient so that a spark will jump from the saw or other charged part of the mechanism a distance of about 2 inches, in practice, more or-less, asthe potential is varied, so that'when the hand or other part of the body of the worker approaches the saw to within a couple of inches thereof, the saw immediately gives out a spark and causes a shock and burn causing him instantly and involuntarily to withdraw his'han-d away from the saw.

The high frequency, high potential used is substantially that used by doctors in the treatment of various maladies, andwhen applied to the human body, the small amount of current which flows at the high frequency high potential has a beneficial effect rather than otherwise upon the body.

The potential being so: high, the conductor leading it to the danger point must be carefully insulated, and it is desirable that it be short. Asshown, I prefer to make the'shaft 3 and flanges 2 holding the saw 1 thereon of non-conducting material. The shaft 3 may be provided with a shoulder against which one flange 2 abuts and the other may be held on and thesaw'clamped by means'of a flanged threaded cap or sleeve 9, screw-threaded upon the end of the shaft, and between the shaft and the flanges .2 forming a seat for the latter. This cap is in contact with the saw 1, and may have formed thereon an exposed contactpoint 32 which projects outwardly and makes contact witha suitable fixed contact member 18 connected with the terminal 17 of the coil.

In order to provide a definite andeffec tive ground, thetable is'preferably covered by a metal plate 25, which extends to withinabout 2 inches of the saw,.and is connected with a metal plate 26 on the floor surrounding the tableon which the operator stands. Tl1e plates;25, '26 are connected electrically, as by Wire to the negative side 19 of the high frequency coil.

While I have described my invention as applied to a wood-cutting saw, it is to be fully understood that it is applicable to any form of dangerous tool where a high frequency high potential can be maintained at or near the danger point and insulated from the ground.

The operation of the device is as follows:

WVhen the saw or other tool is started up for use, the current is also caused to flow worker in any way. The operator stands upon plate 26 and in feeding thebwork to the sawhis hand generally touches plate 25, both 'of these being connected to the negative of the high frequency coil; thus the operator is grounded. If, and when, hisQhand or other part of his body approaches within a predetermined distance, say two inches, more or less, ofthe saw, due to the high frequency, high potential of the saw, a spark jumps from the saw to the hand or nearestv part ofthe body-of the worker, giving him a shock or burning sensation which causes his muscles to involuntarily contract, and causes him to withdraw from danger on receipt of'this warning and before he is hurt.

'Having. now described my invention, I claim and desire to secure by Letters Patent:

1. The method of guarding a dangerous tool which consists in insulating said tool from the ground, and applying a high frequency, high electrical potential thereto.

2. The combination comprising a tool, means for applying a high frequency, high electrical potential to said tool, and means for insulating said tool from the ground.

3. The combination comprising a cutting vor other: dangerous. tool, and means for maintaining a high frequency, high electrical potential adjacent the danger point,

4. The combination comprising a cutting or other dangerous tool, a source of electric current, means for increasing the frequency and stepping up said current to a high frequency, high electrical potential, a terminal insulated from the ground disposed adjacent'the danger point, and a connection be tween. said means and said terminal.

5. The combination comprising a circular sa a ta le and: frame o whi h sai saw is insulated and revolubly mounted, and means for applying a high frequency, high electrical potential to said saw.

6. The combination comprising a circular saw, a table and frame at least partly of insulating material on Which said saw is revolubly mounted, and means for providing a high frequency, high electrical potential adjacent the cutting edge of said saW.

7. The combination comprising a circular saw, a table and frame upon which said saw is mounted and insulated from the ground, means for applying a high frequency, high electrical potential to said saw, a conducting plate for the operator to be in contact with, and a ground connection from the said means for applying the high frequency, high electrical potential leading to said plate.

8. The combination comprising a circular saw, a table and frame upon which said saW is revolubly mounted and insulated from the ground, a conducting plate upon the surface of said table approaching to Within a few inches of said saw, and means grounded upon said plate for applying a high frequency, high electrical potential to said saw.

9. The combination comprising a circular saw, atable and frame upon which said saw is revolubly mounted and insulated from the ground, a conducting plate upon the surface of said table approaching to Within a feW inches of said saw, a further plate surrounding said table for the operator to stand upon, and means grounded upon said plates for applying a high frequency, high electrical potential to said saw.

In testimony whereof I have signed my name to this specification.

ROBERT L. MORROW. 

